(a) Field of the Invention
The present invention relates to a communication method using the mobile IPv6 (Internet Protocol version 6). More specifically, the present invention relates to an NAT-PT applied communication method in the IPv6 network.
(b) Description of the Related Art
IP networking represented by mobile communication and the Internet has become the most popular issue in the IT industry.
Mobile communication has been popularized because of fast distribution of wireless mobile communication nodes other than wired nodes, and it has been facing a new trend together with network unification movements on the basis of recently issued wireless LAN and IPs.
Also, IP networking is expected to cause great demands of IP addresses because of unification of the IP-based networks, and accordingly, the IPv6 which is the next version of the IPv4 has been developed in preparation for the demands.
Respective nodes are identified by IP addresses in the IP network, and the addresses are varied according to moving to an area. Therefore, it is needed for a node to be able to move to another area without changing the IP address in the current communication process because of the characteristic of the IP network which communicates by using the IP addresses as identifiers of the respective nodes. Without this ability, the communication is disabled when the node leaves the area in which the node can perform communication with the IP address possessed by the node.
The mobile IP technology has been proposed in order to solve the problem. When a communicating node (referred to as an MN (mobile node) hereinafter) moves to a new area, an IP address (referred to as a COA (care of address) hereinafter) appropriate for the new area is newly allocated to the MN in addition to the IP address currently in use.
The biggest problem with introducing the IPv6 because of address exhaustion in the IPv4 is that it is substantially impossible to exchange a lot of IPv4-based Internet nodes for the IPv6 nodes at once. Therefore, a technique for linking the IPv6 nodes and the IPv4 nodes and thereby preventing coexistence of the IPv6 and IPv4 nodes while transferring to the IPv6 nodes is required, which is the NAT-PT (Network Address Translation-Protocol Translation.)
The NAT-PT belongs to conversion techniques executed by the NGTrans (Next Generation Transition) working group, based on the NAT (Network Address Translation) technique. A major purpose of the NAT-PT is to convert IPv6 headers and IPv4 headers and allow communication between IPv6 nodes and IPv4 nodes. In order to achieve this purpose, an NAT-PT box is provided between the IPv6 network and the IPv4 network, and it mutually converts IPv6 packets and IPv4 packets. The NAT-PT technique is performed normally in most conventional protocols, but it does not consider the environment of the mobile IPv6.
The mobile IPv6 technique is to maintain communication without disconnection when an MN which performs IP communication on the IP network moves to another area.
To achieve this, the MN receives and uses a new address available in another area each time it moves thereto, and the MN transmits and receives information on the newly allocated address (i.e., a COA) to/from a CN (correspondent node) in order to perform communication by using the COA. Also, the MN combines the COA and an HA (home address) originally possessed by the MN to use an IPv6 extended header in order to maintain the communication in the new area. However, in this case, the usage of the mobile IPv6 basically assumes that both nodes are IPv6 nodes with no consideration of usage of the NAT-PT applied network.
Therefore, realization of the NAT-PT may have a problem when an IPv6 node attempts communication with an IPv4 node by using a mobile IP in the NAT-PT environment, since the communication between the IPv6 node and the IPv4 node is possible through the NAT-PT box but the CN communicated by each node is actually a different node even if it seems to use an IP of the same version through a header conversion. Accordingly, the mobile IPv6 mechanism cannot be normally operated unless the NAT-PT box which controls the conversion therebetween performs additional processes when the mobile IPv6 node follows the mobile IPv6 mechanism and is operated.